Questions about the installation of /e/ on oneplus 3T


I installed /e/ on an old Oneplus 3T today.
I followed the installation process here :
In the section about flash recovery, it’s written

fastboot flash boot twrp-x.x.x-x-oneplus3.img

This command seem to prepare to boot the device in twrp but not to install twrp, because after installation of /e/ at next reboot to recovery, I still had the recovery from Oneplus.
I realized that the command for install recovery is

fastboot flash recovery twrp-x.x.x-x-oneplus3.img

As a result, I wonder if I did the right thing.
Can we install /e/ and keep the Oneplus recovery ?

Also, on the download page of /e/, there is a specific recovery (recovery-e-0.13-q-2020120789006-dev-oneplus3.img), so I tried it too.
Which one is better to keep for future updates ?
twrp or the specific recovery of /e/ ?

I noticed that with TWRP, the adb sideload finished with

adb sideload 
Total xfer: 1.01x

And with the custom recovery the command finished with :

adb sideload 
serving: ''  (~47%)    adb: failed to read command: Success

But it seems to work anyway.


Personally, as of now I prefer TWRP, as it has more features.
I think you can chose the one you prefer: the choice shouldn’t cause any problem with the system.


Updates with /e/ custom recovery is more user friendly (nice animation),
but I realized, by testing with both recovery, that only TWRP could be protected by pattern.
So I chose TWRP.